JPH0358103B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a positive resist material for high-energy beam lithography and a method for forming a fine resist pattern using the same. Conventionally, photoresists using visible light or near ultraviolet light have been used as pattern forming materials in technical fields such as masking and semiconductor manufacturing, and such resists have been sufficient to form openings on the order of several μm. However, in recent years, as electronic components have become lighter and larger in capacity, patterns have become finer, and it has become necessary to have openings on the order of several μm or less, particularly 1 μm or less. In order to form such fine patterns on the order of several μm or submicron, conventional photoresist materials cannot be used, so high-energy rays such as far ultraviolet rays with shorter wavelengths, X-rays, and electron beams are used. Resist materials have been developed that utilize this technology, and it has become possible to form fine patterns on the submicron order. One of the most widely used resist materials is polymethacrylate (hereinafter referred to as PMMA). Although PMMA has extremely high resolution, it has low sensitivity (for example, 1300 mJ/cm ² for Mo L-ray, which is a soft X-ray,
(1×10 ⁻⁴ C/cm ² ) for electron beams, and therefore requires a long time to form a pattern. In addition, attempts have been made to use certain polyfluoroalkyl methacrylates as resist materials for high-energy rays (Japanese Patent Publication No. 55-24088
Although these resist materials have improved sensitivity, which is a drawback of PMMA, when developing certain types of substrates such as silicon, the developer may penetrate between the resist pattern and the resist pattern. Problems caused by poor adhesion, such as peeling off or lifting of the pattern, resulting in a decrease in precision, such as the dimensions of the pattern on the substrate obtained by etching becoming larger than the specified dimensions. There is a point. Such defects may not be fully recovered even by post-baking. The present inventors have conducted intensive research to overcome the drawbacks of these conventional resist materials, and as a result, the general formula (): (In the formula, R ₁ represents a methyl group, an ethyl group, a group in which at least one of their hydrogen atoms is substituted with a halogen atom, a halogen atom, or a hydrogen atom, and R ₂ represents a divalent group having 1 to 6 carbon atoms. (represents a hydrocarbon group, R _f represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom) and a fluoroalkyl acrylate represented by the general formula (): (In the formula, R ₃ represents a hydrogen atom, a methyl group, or an ethyl group.) A copolymer obtained by copolymerizing acrylamide has high sensitivity and resolution, and has excellent adhesion. It has been found that it is an extremely excellent positive resist material for pattern formation. Specific examples of the compound represented by the general formula () include those represented by the following chemical formula. CH ₂ =C(CH ₃ )COOCH ₂ CF ₂ CHF ₂ CH ₂ =C(CH ₃ )COOCH ₂ CF ₂ CF ₂ CF ₂ CHF ₂ CH ₂ = CClCOOCH ₂ CF ₂ CHF ₂ CH ₂ = C(CH ₃ ) COOCH ₂ CF ₂ CHFCF _{3 CH2} =C( _CH3 ) _{COOCH2CH2CF2CF2CF3CH2} =C( _{CH3 ) COOCH2CH2} ( _{CF2CF2 ) CF3General formula} ( _{) in the} copolymer related to _the present invention The ratio (mole ratio) of the compound represented by and the compound represented by the general formula () is 60:40 ~
99.9:0.1, especially preferably 80:20 to 99.9:0.1. The adhesion of the copolymer improves as the proportion of the compound represented by the general formula () increases, but the sensitivity and resolution decrease. Within the above ratio range, the sensitivity and resolution do not deteriorate to the extent that they become a practical problem, and the adhesion is also within a sufficient range. In addition, the weight average molecular weight is
10,000 to 2,000,000, preferably 50,000 to 1,000,000 are used. As the molecular weight becomes higher, the difference in dissolution rate in a solvent between the irradiated portion and the non-irradiated portion of the high-energy ray becomes larger, and the sensitivity and resolution improve. The copolymer used in the present invention can be produced by bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. of the compound represented by the general formula () and the compound represented by the general formula () in the presence of a conventional polymerization catalyst. This can be carried out by copolymerization using any polymerization method. The degree of polymerization can be adjusted by a conventional method by changing the amount of polymerization catalyst added, reaction temperature, etc. A method for forming a resist film of the copolymer on the substrate can be performed by a general resist film forming method. That is, the copolymer is dissolved in a solvent such as an aliphatic ketone, an aliphatic alcohol, an aliphatic ester, an aliphatic ether, an aromatic hydrocarbon, an alicyclic ketone, a halogenated hydrocarbon, or a mixture thereof to prepare a resist solution. A resist film can be formed by coating the resist solution onto a substrate using a spin coater or the like, and then completely evaporating the solvent by air drying, heating drying, or the like. The substrate that can be used is not particularly limited, and various substrates such as a chrome mask substrate, silicon, silicon oxide, silicate glass, silicon nitride, aluminum, titanium, and gold can be used in the present invention, and the present invention can be applied to any of the substrates. The resist film obtained by this method shows high adhesion. A fine resist pattern can be formed by irradiating the resist film with high-energy rays to draw a pattern and then developing it using a developer. Examples of high-energy rays used for pattern drawing include electron beams, ultraviolet rays of 300 nm or less, deep ultraviolet rays, and X-rays. The developing solution is a solvent in which, in the resist film made of the copolymer, the dissolution rate of the part whose molecular weight has been reduced by irradiation with high-energy rays and the originally high-molecular-weight part which has not been irradiated with high-energy rays is significantly different. used. Such solvents include (A) one or a mixture of two or more alcohols having 2 to 8 carbon atoms; or (B) () one or more alcohols having 2 to 8 carbon atoms. Examples include a mixture consisting of a mixture and () a mixture of one or more hydrocarbons having 5 to 11 carbon atoms, or water. Among (B), () is preferably isopropyl alcohol or normal propyl alcohol;
is hexane, heptane, octane, nonane,
benzene, cyclohexane or water.
The mixing ratio of the solvents listed in () and the solvents listed in () of (B) can be appropriately selected and determined depending on the molecular weight of the copolymer and the desired sensitivity. Further, the developing temperature and time may be appropriately determined depending on the type of developer and the molecular weight of the copolymer. Finally, the desired fine resist pattern is formed by drying and baking the irradiated object after development. Next, the present invention will be explained in more detail with reference to reference examples and examples, but the present invention is not limited only to these examples. Reference Example 1 To 12 parts of methacrylic acid chloride (parts by weight, the same applies hereinafter) and 60 parts of 2,2,3,4,4,4-hexafluorobutyl alcohol, 0.1 part of hydroquinone dimethyl ether as a polymerization inhibitor was added, and 90~ Heated at 100°C for 3 hours. The reaction product mixture was distilled to give 2,2,3,4,4,4-hexafluorobutyl methacrylate (hereinafter referred to as
15 parts (called HFBMA) (boiling point: 60-63
℃/20mmHg). Next, to 99 parts (97.1 mol parts) of HFBMA, 1 part (2.9 mol parts) of methacrylamide (hereinafter referred to as MAA) and azobisisobutyronitrile (hereinafter referred to as ``MAA''),
AIBN) 0.1 part, dodecyl mercaptan
0.025 parts and 100 parts of methyl isobutyl ketone were added, mixed, degassed, and the mixture was heated at 60°C for 24 hours.
Copolymerized over time. Acetone was added to the reaction product mixture to make a homogeneous solution, and then petroleum ether was added to precipitate it, yielding 93 parts of a copolymer. Analysis of this copolymer by pyrolysis gas chromatography revealed that the monomer unit of MAA was
It was confirmed that the content was 3.0 mol%, and copolymerization occurred at approximately the charging ratio. Intrinsic viscosity [η] determined at 35℃ using this copolymer as a methyl ethyl ketone solution
was 0.39. Further, the weight average molecular weight determined by gel vermiaction chromatography was approximately 550,000. Example 1 46 parts of methyl isobutyl ketone was added to 4 parts of the copolymer obtained in Reference Example 1 to prepare a uniform resist solution. The resist solution was spin-coated onto a silicon wafer until the film thickness was 0.5μ.
Coated so that it becomes m, and then heated at 140℃.
The solvent was evaporated by heating for 30 minutes, and then cooled to room temperature to form a resist film. Next, using an ERE-302 electron beam lithography system (manufactured by Elionix Co., Ltd.), each sample with the resist film was exposed to an electron beam at an acceleration voltage of 20 kV (current 1 x 10 ^-9 A) for 0.08 seconds (electron dose 1.9 ×
10 ^-7 C/cm ² ) to 125 seconds (electron dose 2.9×10 ^-4 C/
cm ² ) and was drawn by irradiating several points. 23 of these samples
The resist pattern was developed by immersing it in a mixed solvent of isopropyl alcohol and n-heptane (volume ratio 85:15) at 0.degree. C. for 90 seconds. This item should be immediately heated to 23°C
- Cleaned by soaking in heptane for 60 seconds. The remaining film thickness of the resist film of the resist pattern obtained in the above manner was measured using a film thickness measuring device (Talystep (manufactured by Bobson, UK)). FIG. 1 shows a characteristic diagram showing the relationship between irradiation time (seconds) and residual film thickness (μm). From FIG. 1, it can be seen that the resist has a sensitivity of 1.2×10 ⁻⁶ C/cm ² and a γ value of 2.62. Next, lines and spaces of 2, 3, and 5 μm were drawn using an electron beam of 0.47×10 ⁻⁶ C/cm ² , and the resulting resist pattern was similarly developed, washed, and dried, and the resulting resist pattern was observed under a 400x optical microscope. Adhesion was evaluated. As a result, it was observed that both patterns were completely adhered to each other. Example 2 Isopropyl alcohol used as developer
An experiment was carried out in the same manner as in Example 1, except that the n-heptane mixed solvent was replaced with isopropyl alcohol containing 1.25% water. As a result, the sensitivity is 1×
10 ⁻⁶ C/cm ² , and the γ value was 2.0. Moreover, the adhesion was very good. Reference Example 2 A copolymer was obtained by carrying out an experiment in the same manner as in Reference Example 1, except that the amount of HFBMA used was 90 parts and the amount of MAA was 10 parts. Example 3 An experiment was conducted in the same manner as in Example 1, except that the copolymer used was replaced with that obtained in Reference Example 2, and the developer was replaced with isopropyl alcohol-n-octane (volume ratio 1:5). . As a result, the sensitivity is 2.9×
10 ⁻⁵ C/cm ² , and the γ value was 1.2. Also, the adhesion was very good. Reference Example 3 99 parts of 2,2,3,3-tetrafluoro-1,1-dimethylpropyl methacrylate was used in place of HFBMA, and 1 part of acrylamide was used in place of MAA.
A copolymer ([η]=1.10) was obtained by conducting an experiment in the same manner as in Example 1 except that 0.05 parts of polymerization initiator was used. Example 4 An experiment was conducted in the same manner as in Example 1, except that the copolymer used was replaced with that obtained in Reference Example 3. As a result, the sensitivity was 2.0×10 ⁻⁴ C/cm ² and the γ value was 1.4. Also, the adhesion was very good. Reference example 4 Methyl methacrylate (hereinafter referred to as MAA)
Add and mix 10 parts of methacrylamide (11.5 mol%) and 0.1 part of AIBN to 90 parts (88.5 mol%),
After degassing, the mixture was copolymerized at 60° C. for 24 hours. Acetone was added to the reaction product to make a homogeneous solution, which was then poured into petroleum ether, the precipitated polymer was collected, vacuum dried, and polymer 85
I got a department. The intrinsic viscosity [η] of this copolymer determined as a solution in methyl ethyl ketone at 35° C. was 1.1. In addition, the weight average molecular weight determined by gel permeation chromatography is approximately 600,000.
It was hot. Reference Example 5 99.15 parts of MMA (99 mol%), 0.85 parts of methacrylamide (1 mol%) and 0.1 part of AIBN were added and mixed, and the same procedure as in Reference Example 4 was repeated to obtain 90 parts of a polymer. "η" of the obtained polymer was determined in the same manner as in Reference Example 4, and the weight average molecular weight was 1.0 and the weight average molecular weight was approximately 500000.
It was hot. Reference Example 6 0.1 part of AIBN was added to 100 parts of MMA and mixed. After degassing, this mixture was polymerized at 60° C. for 24 hours. Acetone was added to the reaction product to make a homogeneous solution, which was then poured into petroleum ether, and the precipitated polymer was collected and vacuum dried to obtain 90 parts of the polymer. The intrinsic viscosity [η] determined at 35° C. of the resulting polymer as a methyl ethyl ketone solution was 1.0.
Furthermore, the weight average molecular weight determined by gel permeation chromatography was approximately 500,000. Example 5 46 parts of methyl isobutyl ketone was added to 4 parts of the copolymer obtained in Reference Example 1 to prepare a uniform resist solution. The thickness of the film is increased by spin coating the resist solution onto a silicon wafer.
Coating to 0.8μm, then 140μm
C. for 30 minutes to evaporate the solvent, and then cooled to room temperature to form a resist film. Next, using the electron beam irradiation device used in Example 1, 400 square patterns each with sides of 1.0 μm, 2.0 μm, 3.0 μm, and 5.0 μm were formed with an electron beam irradiation dose of 2.0 × 10 ^-6 C/cm ² . Electron beam writing was performed as shown in the image, and it was developed for 90 seconds (at 23°C) with a mixed solution of isopropyl alcohol/n-heptane (volume ratio 85:15), and then rinsed (at 23°C for 60 seconds in n-heptane). The dried material was observed with an optical microscope, and the survival rate of the patterns of each size formed ((number of remaining patterns/400) x
100), all the patterns remained and the survival rate was 100%. Example 6 An experiment was conducted in the same manner as in Example 5, except that the copolymer, developer, rinse solution, and electron beam irradiation amount were changed to those shown in Table 1, and each resist was tested for each pattern of each size. The survival rate was calculated. The results are shown in Table 1. Comparative Example 1 Using a homologous polymer of HFBMA ([η] 0.8, weight average molecular weight approximately 800,000), a homogeneous solution was prepared by adding 46 parts of methyl isobutyl ketone to 4 parts of this polymer. The resist solution was spin-coated onto a silicon wafer to a film thickness of 0.8 μm.
Coat it so that it becomes
Prebaking for 1 minute to evaporate the solvent,
A resist film was formed by cooling to room temperature. Next, adjust the developer, rinse solution, and electron beam irradiation amount to the first
An experiment was conducted in the same manner as in Example 5, except that the samples were changed to those listed in the table, and the survival rate for each pattern of each size was determined. The results are shown in Table 1. Comparative Examples 2 to 4 10 parts of the polymer shown in Table 1 was dissolved in 90 parts of ethyl cellosolve acetate to make a homogeneous solution, and then coated on a silicon wafer to a thickness of approximately 1 μm, and pretreated at 200°C for 30 minutes. Perform baking;
A resist film with a thickness of 0.8 μm was obtained. An experiment was conducted in the same manner as in Example 5, except that the developer (development conditions were 23°C for 120 seconds) and rinse solution were replaced with those shown in Table 1. I asked for The results are shown in Table 1.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the relationship between electron beam irradiation time and residual film thickness.

Claims (1)

[Claims] 1 General formula (): (In the formula, R ₁ represents a methyl group, an ethyl group, a group in which at least one of their hydrogen atoms is substituted with a halogen atom, a halogen atom, or a hydrogen atom, and R ₂ represents a divalent group having 1 to 6 carbon atoms. (represents a hydrocarbon group, R _f represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom) and a fluoroalkyl acrylate represented by the general formula (): (In the formula, R ₃ represents a hydrogen atom, a methyl group, or an ethyl group.) A resist material made of a copolymer with acrylamide. 2 The molar ratio of the fluoroalkyl acrylate represented by the general formula () to the acrylamide represented by the general formula () is 60:40 to 99.9:
Claim 1 consisting of a copolymer of 0.1
Resist materials listed in section. 3 The molar ratio of the fluoroalkyl acrylate represented by the general formula () to the acrylamide represented by the general formula () is 80:20 to 99.9:
Claim 1 consisting of a copolymer of 0.1
Resist materials listed in section. 4 The weight average molecular weight of the copolymer is from 10,000 to
20000000. The resist material according to claim 1, 2 or 3. 5 The weight average molecular weight of the copolymer is 50,000 to 50,000.
10000000. The resist material according to claim 1, 2 or 3. 6 General formula (): (In the formula, R ₁ represents a methyl group, an ethyl group, a group in which at least one of their hydrogen atoms is substituted with a halogen atom, a halogen atom, or a hydrogen atom, and R ₂ represents a divalent group having 1 to 6 carbon atoms. (represents a hydrocarbon group, R _f represents an alkyl group having 1 to 15 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom) and a fluoroalkyl acrylate represented by the general formula (): (In the formula, R ₃ represents a hydrogen atom, a methyl group, or an ethyl group) A resist film made of a copolymer obtained by copolymerizing acrylamide is irradiated with high-energy rays and then developed. A method for forming a fine resist pattern. 7. The developing agent is an alcohol having 2 to 8 carbon atoms.
7. The method for forming a fine resist pattern according to claim 6, wherein the method is carried out using a species or a mixture of two or more species as a developer. 8. A mixture in which the development is made of () one or a mixture of two or more alcohols having 2 to 8 carbon atoms and () a mixture of one or more hydrocarbons having 5 to 11 carbon atoms or water. 7. A method for forming a fine resist pattern according to claim 6, which is carried out using as a developer. 9 The development is performed using () isopropyl alcohol or n-propyl alcohol and () hexane, heptane, octane, nonane,
7. The method for forming a fine resist pattern according to claim 6, wherein the method is carried out using a mixture of benzene, cyclohexane, or water as a developer.